A new exhaust for an old boat. - SailNet Community
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post #1 of 27 Old 12-18-2016 Thread Starter
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A new exhaust for an old boat.

My 1961 Alden Challenger, now on it's 3rd engine, has the original exhaust. Or, I should say, 'had'.

These old double wall pipe exhausts are considered dangerous because there is no way to tell when the inner pipe will fail thus allow the cooling raw water in the outer jacket, to flow back into the engine on shut down. Catastrophic failure. After haul out, I began cutting the old exhaust out of the boat.



After my first cut with a new Sawzall blade, my first thought was, "What have I done?" It turns out the pipe was very thick, very solid copper and some bronze. Further dissection I found beyond the high loop where the raw water exits and enters a 1961 cast iron Maxim Silencer muffler (very effective), everything was solid. It doesn't matter now. I've got to install a modern water lift muffler system.

I've researched and researched. A particularly helpful article is one from Good Old Boat that's online.

Good Old Boat - Cool and Quiet and trouble-free article

At this point: I've ordered a Centrex waterlift with a larger volume and a water injection elbow.

This is a shot from just forward of the steering quadrant in my engine compartment. The blue horizontal line is roughly the water line. I plan to mount the muffler (blue square) after of the engine and alongside the transmission. The thick blue line is roughly where I plan to run the 2 3/8" exhaust hose.



Here's a sketch from the side: The plan is to install a pipe riser off the exhaust manifold to raise the water injection elbow, and to install a vented loop(just below the cockpit sole or possibly higher if I can fit it), on the raw water line.



It would be nice to run the exhaust hose up into a cockpit locker - which could put it at it's highest point - but I don't want the hose in the access area(my last boat was that way).

I think this should work but any ideas would be appreciated. Thanks!

Tom Young sailing a 1961 38' Alden Challenger, CHRISTMAS out of
Rockport, Maine.
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post #2 of 27 Old 12-18-2016
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Re: A new exhaust for an old boat.

I would try to make the engine to muffler loop a little higher. Back flow worries me. I've only done this once so I'm far from an expert. My last boat had a second inline muffler back about where your muffler used to be and it was near silent.

Again, I am no expert!

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post #3 of 27 Old 12-18-2016
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Re: A new exhaust for an old boat.

Tom, I would have to agree with Rob, remember that with your boat heeled over that water line on the leeward side will be considerably lower than when at rest. also, get your vented loop up higher to prevent back siphoning. Beautiful boat by the way. Good luck.
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post #4 of 27 Old 12-18-2016
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Re: A new exhaust for an old boat.

Tom, can you route the hose higher by going around the cockpit? How twas in my boat. One lift through one inverted loop I think may be best.

what engine is that Tom?

"Next best thing to not having a boat? The knowledge from having one!" Denise, Bristol PA, On Tidal Delaware River, Anchor Yacht Club.
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post #5 of 27 Old 12-18-2016
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Re: A new exhaust for an old boat.

I would not raise the exhaust elbow as it does not let the engine manifold drain if water gets in there. most all the new engines have the manifold at the high point and drain down to the water lift. the hose after the exhaust elbow should go down to the water lift so all the water will drain to the water lift at shut down. if it loops up you will get drain back to the engine. that is why the water lift is there to prevent drain back to the engine.
you can make a complete 360 degree loop up in the stern to prevent the ocean from coming back in. a 360 loop is easier to do then the up and then down bends.

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post #6 of 27 Old 12-18-2016
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Re: A new exhaust for an old boat.

Id recommended a 'heat-riser' between the engine exhaust outlet and 'before' the exhaust leg that enters the water-lift. This will help to insure against 'back flow' from a seaway into the engine. All you have to do is locate the water injection port of the 'heat-riser' as physically as high as possible 'up' from the exhaust outlet on the stern.

Pros -
Can be built from common black iron pipe/fittings. Most engine supply sources can provide the engine manifold to black iron threaded flange.
Threaded connections can be sealed via 'muffler cement'.
Will allow constant attempts to start an engine without the requirement of shutting down engine raw water cooling

Cons -
The un-wetted section of the heat riser must be covered with thick application 'lagging' (fiberglass, rock wool, etc.) to retard heat transfer into the engine, etc. spaces.
The lagged area of pipe will have relatively shorter service life due to the high heat. (Marine engine supply sources all sell such 'lagging'.)
The interior space containing the heat-riser will become heated and may need to be air-vented.
You'll have to build a 'constraint' at the top of the heat riser assembly to prevent/dampen 'vibrations' of the heat riser .... usually direct connected to the 'engine block'; the final structure including the heat riser will be a 'triangle'.
"When" the engine manifold eventually develops a pin-hole between the gas side and the water side, that leaked water will definitely retro-flow into the engine - therefore periodic 'pressure testing' of exhaust manifold is needed ... probably 'yearly' after the first 5 years of the manifolds service life.

For the old copper-jacketed exhaust ... consider to have it inspected via ultrasound then 'pressure-hold' methods to analyze wall thickness, water integrity, etc.; and if still has 'meat' (corrosion allowance), braze it back together and use it. Any reliable 'ASME code' heat exchanger shop can do this for you. Bath, ME / Portsmouth NH should have a lot of such shops. Be sure to use phos-copper for the brazing.
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Last edited by RichH; 12-18-2016 at 01:00 PM.
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post #7 of 27 Old 12-18-2016 Thread Starter
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Re: A new exhaust for an old boat.

Quote:
Originally Posted by RobGallagher View Post
I would try to make the engine to muffler loop a little higher. Back flow worries me. I've only done this once so I'm far from an expert. My last boat had a second inline muffler back about where your muffler used to be and it was near silent.

Again, I am no expert!
Flooding the engine worries me, too! Back flooding from the stern outlet (if that's what you mean), is the only area I'm not worried about.

As long as I keep the last high loop as high or higher(which I think I can gain a couple inches) than the jacketed original exhaust, that's been proven.

The old exhaust had no riser - no muffler volume at the engine - just a straight shot into the exhaust manifold. Even a few cups would have flooded the engine. It's never happened so I'm confident in that(it's really high above the waterline).

Thanks!

Tom Young sailing a 1961 38' Alden Challenger, CHRISTMAS out of
Rockport, Maine.
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Re: A new exhaust for an old boat.

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Originally Posted by flyrod View Post
Tom, I would have to agree with Rob, remember that with your boat heeled over that water line on the leeward side will be considerably lower than when at rest. also, get your vented loop up higher to prevent back siphoning. Beautiful boat by the way. Good luck.
I will raise the vented loop. I think I may go into one of the cockpit lockers in which case, I'll get the vented loop at bridge deck height.

Thanks!
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Tom Young sailing a 1961 38' Alden Challenger, CHRISTMAS out of
Rockport, Maine.
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Re: A new exhaust for an old boat.

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Originally Posted by deniseO30 View Post
Tom, can you route the hose higher by going around the cockpit? How twas in my boat. One lift through one inverted loop I think may be best.

what engine is that Tom?
I could route it outboard beneath the port cockpit seat height, which is better at rest. But on a heel, I calculate it's actually lower than the cockpit sole. But I'll check it out. Thanks Denise.

The engine is a Nissan SD 22 4 cylinder diesel. It's the boats second one in fact (I put this one in myself - found a lightly used SD in a Datsun PU).

They were designed for industrial applications, water pumps and generators in the 60's-70's. Chrysler marine-ized the SD's in the 70's.

In the 80's Datsun replaced the manual governors (keeps rpms at a high of about 2200RPM) with a faster version that allowed them higher RPMs, and put them in Datsun and Nissan PU trucks. Somewhere in between, they were used in Fork lifts.

Tom Young sailing a 1961 38' Alden Challenger, CHRISTMAS out of
Rockport, Maine.
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post #10 of 27 Old 12-18-2016 Thread Starter
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Re: A new exhaust for an old boat.

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Originally Posted by overbored View Post
I would not raise the exhaust elbow as it does not let the engine manifold drain if water gets in there. most all the new engines have the manifold at the high point and drain down to the water lift. the hose after the exhaust elbow should go down to the water lift so all the water will drain to the water lift at shut down. if it loops up you will get drain back to the engine. that is why the water lift is there to prevent drain back to the engine.
you can make a complete 360 degree loop up in the stern to prevent the ocean from coming back in. a 360 loop is easier to do then the up and then down bends.
I'm worried about (per the GOB article) having the water injection too close to exhaust manifold outlet. Apparently too close can cause problems. And I have to use a 'riser' to get the injection point a safe distance away (if you believe the above).

Thanks, I'm considering all points.

Tom Young sailing a 1961 38' Alden Challenger, CHRISTMAS out of
Rockport, Maine.
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